CN212988475U

CN212988475U - Gas flowmeter

Info

Publication number: CN212988475U
Application number: CN202021792755.7U
Authority: CN
Inventors: 周昌全; 冯勇; 杨荣中; 江苏刚; 黄立基
Original assignee: Sixiang Micro Electromechanical Hangzhou Co ltd
Current assignee: Sixiang Micro Electromechanical Hangzhou Co ltd
Priority date: 2020-08-25
Filing date: 2020-08-25
Publication date: 2021-04-16
Anticipated expiration: 2030-08-25

Abstract

The utility model provides a gas flowmeter relates to the gas metering equipment field, designs for solving the unsafe problem of gas trade measurement that current gas metering mode exists. The gas flowmeter comprises a metering unit and a communication unit, wherein the metering unit comprises a gas flow channel, an MEMS sensor assembly and a control module, and the gas flow channel provides a stable flow field of a detected gas; the MEMS sensor assembly comprises an MEMS thermal time-of-flight sensor and a combustible gas concentration sensor which are electrically connected with the control module, the MEMS thermal time-of-flight sensor comprises a first heating element and a plurality of thermosensitive elements which are sequentially arranged along the gas flow direction, the distance between at least two of the thermosensitive elements and the first heating element is in non-integral multiple relation, and the combustible gas concentration sensor is configured to measure the concentration of components with combustion values in gas; the communication unit is electrically connected with the control module. The utility model provides a gas flowmeter metering result is accurate.

Description

Gas flowmeter

Technical Field

The utility model relates to a gas metering equipment field particularly, relates to a gas flowmeter.

Background

The promotion of the use of clean energy, in which natural gas has been increasingly used as clean energy for civil kitchenware and heating, has been one of the key tasks of countries in the world to cope with global climate change. At present, in the level trade metering of urban civil natural gas, the metering mode adopted by the current regulations in all countries/regions is volume metering, the metering technology is a mechanical technology on the basis of the measuring principle, and the metering value changes along with the change of temperature and pressure. However, the heat value of natural gas is actually consumed by consumers instead of the volume of the natural gas, and the heat value of the natural gas depends on components with combustion values in the natural gas, so that when the components of a gas supply source are changed by using the same volume metering, the volume cost paid by the consumers is different from the heat value of the natural gas, and the unfair phenomenon of the natural gas in the process of metering trade exists, and the benefit of the consumers is influenced.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a gas flowmeter to solve the unsafe technical problem of gas trade measurement that current gas measurement mode exists.

The utility model provides a gas flowmeter, including metering unit and communication unit.

The metering unit comprises a gas channel, an MEMS (micro electro Mechanical Systems) sensor assembly and a control module, wherein the gas channel provides a stable flow field for the detected gas; the MEMS sensor assembly comprises a MEMS thermal time-of-flight sensor and a combustible gas concentration sensor which are electrically connected with the control module, the MEMS thermal time-of-flight sensor comprises a first heating element and a plurality of thermosensitive elements which are sequentially arranged along the gas flow direction, the distance between at least two of the thermosensitive elements and the first heating element is in non-integral multiple relation, and the combustible gas concentration sensor is configured to measure the concentration of a component with a combustion value in gas; the communication unit is electrically connected with the control module.

The gas flow meter further comprises a gas buffer chamber, the gas buffer chamber is provided with an inlet and an outlet, the gas flow channel is arranged in the gas buffer chamber, the gas outlet end of the gas flow channel is connected and communicated with the outlet, and the gas inlet end of the gas flow channel extends into the gas buffer chamber; the inlet and the outlet are opened on the same surface of the gas buffer chamber.

Furthermore, the MEMS sensor component further comprises a support plate, the MEMS thermal time-of-flight sensor and the combustible gas concentration sensor are fixedly arranged on the support plate, the support plate is inserted in the gas flow channel, the MEMS thermal time-of-flight sensor is located in the gas flow channel, and the combustible gas concentration sensor is located outside the gas flow channel.

Further, the gas flow channel is in a venturi shape, and the MEMS thermal time-of-flight sensor is located in the center of the throat part of the gas flow channel.

Furthermore, a gas collecting hood is fixedly arranged on the outer wall of the gas flow channel, a hood opening of the gas collecting hood faces the cavity of the gas buffer chamber, a gas collecting cavity is formed in the gas collecting hood, the gas collecting cavity is communicated with the gas flow channel through an opening, and the support plate is inserted into the opening.

Further, a filter is arranged at the opening and is configured to filter the gas flowing from the gas flow passage to the gas collecting cavity.

Furthermore, the gas flow channel comprises a main flow channel and a connecting flow channel which are sequentially arranged along the gas flowing direction, the main flow channel is in a straight tube shape, the connecting flow channel is in a bent tube shape, and the connecting flow channel is used for being connected with the outlet; the MEMS thermal time-of-flight sensor is located within the primary runner.

Further, be provided with flow distributor in the sprue, flow distributor includes a plurality of coaxial pipes of establishing of overlapping in proper order, and arbitrary adjacent two the interval of coaxial pipe is not more than to be located the most central position the internal diameter of coaxial pipe.

Further, the axial length of the flow distributor is not less than 1/3 of the axial length of the primary flow passage.

Further, the gas flow meter further includes an electrically operated valve provided at the inlet, the electrically operated valve being electrically connected to the communication unit, the electrically operated valve being configured to cut off supply of gas at the inlet when a condition is set.

Further, a flow field regulator is arranged at the air inlet end of the gas flow channel.

Further, the communication unit includes protecgulum, back lid and display module, the protecgulum with the back lid is connected and is formed and hold the chamber, the display module set up in hold in the chamber, the protecgulum open be equipped with the relative first window of display module, first window department covers has transparent panel, wherein, transparent panel has the data and prevents falsifying the function.

Further, the communication unit further comprises a battery power supply module, the battery power supply module is arranged in the accommodating cavity, a second window opposite to the battery power supply module is further formed in the front cover, and a battery chamber cover is detachably covered at the second window.

Furthermore, the MEMS thermal time-of-flight sensor also comprises a first substrate, the number of the thermosensitive elements is two, and the first heating element and the two thermosensitive elements are fixedly arranged on the first substrate; the first substrate is further provided with a first temperature sensing element configured to sense an ambient temperature of the gas, and the first temperature sensing element is electrically connected with the control module.

Further, the first base body is further provided with a wake-up element, the wake-up element is electrically connected with the control module, and the wake-up element is configured to wake up the control module when the change of the gas temperature is sensed.

Further, the combustible gas concentration sensor comprises a second substrate, and a combustible gas concentration sensing element, a second heating element and a second temperature sensing element which are all arranged on the second substrate, wherein the second heating element and the second temperature sensing element are all electrically connected with the control module.

The utility model discloses the beneficial effect that gas flowmeter brought is:

the principle of using the gas flowmeter to measure the gas flow is as follows: the gas sequentially passes through the first heating element and the plurality of thermosensitive elements in the flowing process of the gas in the gas flow channel, and the flow speed of the gas in the gas flow channel can be obtained by combining the time difference of sensing the gas by each thermosensitive element due to the known distance from each thermosensitive element to the first heating element, so that the volume flow of the gas can be obtained according to the flow area of the gas flow channel; meanwhile, along with the flowing of the gas in the gas flow channel, each thermosensitive element can also measure the temperature value of the gas at the current position, and the number of molecules contained in the gas at the moment is obtained according to the attenuation of the temperature and the value corresponding to the reference standard device, so that the mass flow rate of the gas is obtained, namely: the MEMS thermal time-of-flight sensor obtains the volumetric and mass flow of the gas. Meanwhile, the values of the temperature of the measured gas measured at different temperature measuring sensors are related to the thermal physical properties of the gas. The MEMS thermal flight time sensor sends the simultaneously measured group of data to the control module, and the control module can calculate the current thermal conductivity, specific heat capacity and other thermal physical parameters of the gas according to the measured volume flow and mass flow.

When the measured gas thermophysical property parameter is different from the value measured in calibration, the control module sends a working signal to the combustible gas concentration sensor, and the combustible gas concentration sensor is used for measuring the concentration of the component with a combustion value in the current gas. Because the single gas with the fixed component combination of the combustion value has unique comprehensive thermophysical parameters and can be converted into a high calorific value. Therefore, the thermal properties of the gas medium can be determined by combining the data measured by the sensors, and at the same time, the higher calorific value of the measured gas can be obtained from the measured proportion of the gas component having the combustion value. And the data measured by the measuring unit is sent to the communication unit, and the communication unit outputs the measured data for trade settlement.

The gas flowmeter utilizes an MEMS thermal time-of-flight sensor to realize measurement of gas volume flow and mass flow, and realizes measurement of thermal physical properties of gas by arranging a plurality of thermosensitive elements at the downstream of a first heating element and enabling distances between at least two thermosensitive elements and the first heating element to be in non-integral multiple relation. And in combination with the measurement of the component with the combustion value by the combustible gas concentration sensor, further obtaining the high calorific value of the gas to be measured. Thus, the gas flowmeter not only can provide the trade metering result meeting the current rate system, but also can be used as a database and a reference for measuring the high calorific value of the gas so as to establish the most fair urban natural trade metering system which is beneficial to urban gas distributors and end users.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a first form of a gas flowmeter according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of a second form of a gas flowmeter according to an embodiment of the present invention;

fig. 3 is an exploded view of a gas flowmeter according to an embodiment of the present invention;

fig. 4 is a schematic structural diagram of a MEMS sensor component of a gas flowmeter according to an embodiment of the present invention;

fig. 5 is a schematic structural diagram of a MEMS thermal time-of-flight sensor of a gas flowmeter according to an embodiment of the present invention;

fig. 6 is a schematic structural diagram of a combustible gas concentration sensor of a gas flowmeter according to an embodiment of the present invention;

fig. 7 is a partial exploded view of a gas meter according to an embodiment of the present invention;

fig. 8 is a side view of a partial structure of a gas flowmeter according to an embodiment of the present invention;

fig. 9 is a partial structural sectional view of a gas flowmeter according to an embodiment of the present invention.

Description of reference numerals:

010-a metering unit; 020-communication unit; 030-sealed cable;

100-gas flow channel; 200-a MEMS sensor assembly; 300-a control module; 400-gas buffer chamber; 500-a flow distributor; 600-an electric valve; 700-a flow field regulator; 800-a display module; 900-battery power module;

110-a main flow channel; 120-connecting the flow channel; 130-an air inlet end; 140-an air outlet end; 150-a gas-collecting hood; 160-opening; 170-corrosion resistant gasket; 180-connecting washer;

210-MEMS thermal time-of-flight sensors; 220-combustible gas concentration sensor; 230-a carrier plate; 240-primary connection pad;

211-a first substrate; 212-a first heating element; 213-a first thermosensitive element; 214-a second heat sensitive element; 215-a first temperature-sensitive element; 216-a wake-up element; 217-first connection pads; 218-a first insulating chamber;

221-a second substrate; 222-a combustible gas concentration sensing element; 223-a second heating element; 224-a second temperature-sensing element; 225-second connection pad; 226-a second insulating chamber;

410-a cartridge body; 420-a cover body; 421-an inlet; 422-outlet; 430-a sealing ring; 440-attachment screws;

510-a coaxial tube;

810-front cover; 811-a first window; 812-a second window; 820-a rear cover; 830-a transparent panel; 840-cell chamber cover;

a-a flow channel space; b-chamber space.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention more comprehensible, embodiments accompanied with figures are described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Fig. 1 is a schematic structural diagram of a first form of a gas flowmeter provided in this embodiment, and fig. 2 is a schematic structural diagram of a second form of the gas flowmeter provided in this embodiment. As shown in fig. 1 and 2, the present embodiment provides a gas flowmeter including a metering unit 010 and a communication unit 020.

Fig. 3 is an exploded view of the gas flowmeter provided in this embodiment, fig. 4 is a schematic structural diagram of a MEMS sensor component 200 of the gas flowmeter provided in this embodiment, and fig. 5 is a schematic structural diagram of a MEMS thermal time-of-flight sensor 210 of the gas flowmeter provided in this embodiment. Specifically, as shown in fig. 3, the metering unit 010 includes a gas flow channel 100, a MEMS sensor assembly 200, and a control module 300, wherein the gas flow channel 100 provides a stable flow field for the detected gas; the MEMS sensor assembly 200 includes a MEMS thermal time-of-flight sensor 210 and a combustible gas concentration sensor 220, both electrically connected to the control module 300, the MEMS thermal time-of-flight sensor 210 including a first heating element 212, a first thermal element 213, and a second thermal element 214 sequentially arranged in a gas flow direction, a distance from the second thermal element 214 to the first heating element 212 being a non-integral multiple of a distance from the first thermal element 213 to the first heating element 212, the MEMS thermal time-of-flight sensor 210 being configured to measure a volume flow rate and a mass flow rate of the gas; the combustible gas concentration sensor 220 is configured to measure the concentration of a component having a combustion value in the gas. The communication unit 020 is electrically connected with the control module 300, and the communication unit 020 is configured to output the metering data.

The principle of using the gas flowmeter to measure the gas flow is as follows: in the process that the gas flows in the gas flow channel 100, the gas sequentially passes through the first heating element 212 and the plurality of heat sensitive elements, and because the distance from each heat sensitive element to the first heating element 212 is known, the flow velocity of the gas in the gas flow channel 100 can be obtained by combining the time difference of the gas sensed by each heat sensitive element, and further, the volume flow of the gas can be obtained according to the flow area of the gas flow channel 100; meanwhile, as the gas flows in the gas channel 100, each thermal element can also measure the temperature value of the gas at the current position, and according to the attenuation of the temperature and the value corresponding to the reference standard, the number of molecules contained in the gas at that time is obtained, so as to obtain the mass flow rate of the gas, that is: the MEMS thermal time-of-flight sensor 210 obtains the volumetric and mass flow of the gas. Meanwhile, the values of the temperature of the measured gas measured at different temperature measuring sensors are related to the thermal physical properties of the gas. The MEMS thermal time-of-flight sensor 210 sends the simultaneously measured group of data to the control module 300, and the control module 300 calculates the current thermal conductivity, specific heat capacity, and other thermal physical parameters of the gas according to the measured volume flow and mass flow.

When the measured gas thermophysical property parameter is found to be different from the value measured during calibration, the control module 300 sends a working signal to the combustible gas concentration sensor 220, and the combustible gas concentration sensor 220 is used for measuring the concentration of the component with the combustion value in the current gas. Because the single gas with the fixed component combination of the combustion value has unique comprehensive thermophysical parameters and can be converted into a high calorific value. Therefore, the thermal physical property of the gas medium can be determined by combining the data measured by the sensors, and at the same time, the higher calorific value of the measured gas can be obtained from the measured proportion of the gas component having the combustion value. The data measured by the measuring unit 010 is sent to the communication unit 020, and the measured data is output by the communication unit 020 for trade settlement.

The gas flowmeter realizes measurement of gas volume flow and mass flow by using the MEMS thermal time-of-flight sensor 210, and realizes measurement of thermal properties of gas by arranging a plurality of thermosensitive elements at the downstream of the first heating element 212 and making the distances between at least two thermosensitive elements and the first heating element 212 be non-integral multiple. In conjunction with the measurement of the component having the combustion value by the combustible gas concentration sensor 220, the higher heating value of the measured gas can be obtained. Thus, the gas flowmeter not only can provide the trade metering result meeting the current rate system, but also can be used as a database and a reference for measuring the high calorific value of the gas so as to establish the most fair urban natural trade metering system which is beneficial to urban gas distributors and end users.

In the working process of the gas flowmeter, the control module 300 obtains raw data from the MEMS thermal time-of-flight sensor 210 and the combustible gas concentration sensor 220, amplifies the raw data, and converts analog data into digital data through a high-precision digital-to-analog converter (ADC) for MCU (micro controller Unit) data processing, wherein the acquired data is compared with data stored during calibration to output correct metering values and thermophysical parameters such as thermal conductivity and specific heat capacity of the gas medium. When the measured gas thermophysical parameter is found to be different from the first measured and stored value (measured value at calibration), the combustible gas concentration sensor 220 will wake up and measure the composition of the current gas. The MCU will then invoke an algorithm to calculate the gas upper heating value. Each such event and corresponding data would be stored in multiple memories of the control module 300 and transmitted simultaneously to a designated data or service center.

It should be further noted that the distance from the first thermosensitive element 213 to the first heating element 212 refers to: the distance from the center position of the first heat sensitive element 213 to the center position of the first heating element 212 in the flow direction of the gas; similarly, the distance from the second thermosensitive element 214 to the first heating element 212 refers to: the distance from the center position of the second heat sensitive element 214 to the center position of the first heating element 212 in the flow direction of the gas.

Specifically, in the present embodiment, the distance between any adjacent two of the first heating element 212, the first thermistor and the second thermistor is between 5 and 500 μm, preferably between 30 and 150 μm. Also, the first heating element 212, the first thermistor, and the second thermistor are all made of temperature sensitive materials, such as: platinum, nickel or doped polysilicon.

In this embodiment, in the MEMS thermal time-of-flight sensor 210, the first thermistor 213 and the second thermistor 214 disposed downstream of the first heating element 212 sense two sets of signals when the gaseous medium carries heat: the total heat of decay and the thermal conduction time of the heat from the first heating element 212 to the first heat sensitive element 213 and the second heat sensitive element 214, respectively. The magnitude of the measured change in heat will depend on the mass flow rate and the thermal properties of the gaseous medium, while the heat conduction time will depend on the flow velocity of the gaseous medium and the thermal properties of the gaseous medium. By simultaneously acquiring the above two sets of parameters, namely: the variation in the heat conduction time and the magnitude of the heat conduction from the first thermo-element 213 to the first heating element 212 and the variation in the heat conduction time and the magnitude of the heat conduction from the second thermo-element 214 to the first heating element 212 make it possible to obtain a mass flow rate, a volume flow rate, and thermophysical properties of the gas medium irrespective of the gas components.

In the MEMS thermal time-of-flight sensor 210, data processing does not require calibration of the thermal responses of the first and

second thermistors

213, 214 and the first heating element 212 in vacuum to record and differentiate complex time responses, because thermal decay and transient time measurements are different, and one of them can be used for calibration when temperature and pressure are maintained at constant values. In this configuration and data acquisition, the gas thermophysical properties do not need to be measured under no-flow or static gas conditions, and the first and

second thermistors

213 and 214 provide additional parameters for data processing to eliminate flow rate effects associated with gas characteristics.

In this embodiment, since the fluid in the closed conduit has a one-dimensional character, the gas flow velocity V associated with the temperature (T) and time (T) transients will depend on the thermal diffusivity (D) and the forced convection equation:

thus, under static conditions or when V ═ 0, the thermal diffusivity can be measured. Since a single natural gas with a fixed combination of components of combustion values has a specific thermal diffusivity and can be converted to a higher heating value, the data directly measured by the MEMS thermal time-of-flight sensor 210 can determine the higher heating value of the gaseous medium. In an actual gas supply, the composition of the gas is not constantly changed, and the gas supply of a specific composition is continued for a certain period of time. In addition, for urban gas applications, natural gas is not used continuously throughout the day, and therefore, once the zero flow rate is measured, the thermal properties of the current gas can be measured.

When two thermosensitive members (a first thermosensitive member 213 and a second thermosensitive member 214) are located at a different distance d from the first heating member 212_iDuring the process, unknown and measurement-related thermal diffusion coefficients can be dynamically eliminated by solving a measurement value equation of each thermosensitive element, and the flow speed and mass flow rate in the closed pipeline, which are unrelated to the gas properties, are obtained:

in the above formula (2), k is a constant and represents the difference coefficient between the sensors.

Preferably, in this embodiment, the first heating element 212, the first thermosensitive element 213 and the second thermosensitive element 214 are all thermistors, and the thermistors are preferably made of temperature sensitive materials such as platinum, nickel or doped polysilicon.

In this embodiment, the first heating element 212 is a micro-heater that is loaded with, for example, a heat pulse, a sinusoidal waveform, or other modulated temperature waveform during operation. Preferably, the first heating element 212 is loaded with a sine wave modulated temperature wave.

It should be noted that, in this embodiment, the sensing process of the MEMS thermal time-of-flight sensor 210 is described only by taking the case where the MEMS thermal time-of-flight sensor 210 includes two thermosensitive elements, but in other embodiments, a plurality of thermosensitive elements may be included, and in this case, the distance between at least two of the plurality of thermosensitive elements and the first heating element 212 is a non-integral multiple.

Referring to fig. 3, in the present embodiment, the gas flowmeter may further include a gas buffer chamber 400, specifically, the gas buffer chamber 400 has an inlet 421 and an outlet 422, wherein the gas flow channel 100 is disposed in the gas buffer chamber 400, the gas outlet 140 of the gas flow channel 100 is connected and communicated with the outlet 422, and the gas inlet 130 of the gas flow channel 100 extends into the gas buffer chamber 400; the inlet 421 and the outlet 422 open to the same surface of the gas buffer chamber 400.

In use, the gas flow meter is configured such that a gas source enters from the inlet 421 and fills the entire gas buffer chamber 400, and then, under the action of pressure, the gas enters the gas flow channel 100 from the gas inlet 130 and flows to the outlet 422 through the gas outlet 140 to supply gas to a user.

Through setting up gaseous surge chamber 400, changed gaseous flow path, realized the buffering to gas to, gas through making in the gaseous surge chamber 400 gets into gas flow channel 100 and for the user side air feed, reduced gaseous through flow area, make gaseous velocity of flow accelerate, thereby guaranteed the sensitivity of MEMS hot time of flight sensor 210 response gas parameter, measuring result is more accurate. In addition, the arrangement of the gas buffer chamber 400 also enables particles or dust impurities mixed in the gas to be settled to the bottom of the gas buffer chamber 400, the gas buffer chamber 400 is used for collection, the influence on the gas supply pipeline caused by the impact of the impurities mixed in the gas on the gas supply pipeline is reduced or even eliminated, meanwhile, the interference of the impurities on the MEMS thermal flight time sensor 210 and the combustible gas concentration sensor 220 is also reduced, the measurement precision is ensured, and the reliability of the gas flowmeter of the embodiment is improved.

In addition, the inlet 421 and the outlet 422 are arranged on the same surface of the gas buffer chamber 400, so that the gas flowmeter of the embodiment is compatible with the existing mechanical connection mode of the utility gas meter, the existing flowmeter can be seamlessly installed and replaced on the existing gas pipeline, and the installation is convenient.

Preferably, in the present embodiment, the gas flow path 100 is located at an upper portion of the gas buffer chamber 400. By the arrangement, the principle that the pressure leads the airflow to rise is well utilized, and effective separation of the gas and the impurities is realized.

Referring to fig. 4, in the present embodiment, the MEMS sensor assembly 200 further includes a carrier plate 230, and specifically, the MEMS thermal time-of-flight sensor 210 and the flammable gas concentration sensor 220 are both fixed to the carrier plate 230, the carrier plate 230 is inserted into the gas flow channel 100, the MEMS thermal time-of-flight sensor 210 is located in the gas flow channel 100, and the flammable gas concentration sensor 220 is located outside the gas flow channel 100.

With the dotted line in fig. 4 as a boundary, the left portion represents the flow passage space a, and the right portion represents the chamber space B, that is: the location of the MEMS thermal time-of-flight sensor 210 within the gas flow channel 100 means that the MEMS thermal time-of-flight sensor 210 is located in the flow channel space a, and the location of the combustible gas concentration sensor 220 outside the gas flow channel 100 means that the combustible gas concentration sensor 220 is located in the chamber space B.

Through setting up MEMS hot time of flight sensor 210 in runner space A for MEMS hot time of flight sensor 210 can measure flowing gas, and measuring result is accurate, through setting up combustible gas concentration sensor 220 in cavity space B, makes combustible gas concentration sensor 220 surrounded by the gaseous medium that is full of gas buffer room 400, thereby can carry out accurate measurement to combustible gas concentration. In addition, the carrier plate 230 is arranged to realize integrated installation of the MEMS thermal time-of-flight sensor 210 and the flammable gas concentration sensor 220, which facilitates the fixation of the MEMS sensor assembly 200 on the gas flow channel 100.

Preferably, in the present embodiment, the gas flow channel 100 is in the shape of a venturi, and the MEMS thermal time-of-flight sensor 210 is located at the center of the throat portion of the gas flow channel 100. In the working process of the gas flowmeter, gas flows through the gas flow passage 100, the gas flow passage 100 is arranged to be in a venturi tube shape, so that the gas obtains better flow stability, and meanwhile, the gas has the highest flow speed when flowing to the throat part of the gas flow passage 100. By extending the MEMS thermal time-of-flight sensor 210 into the center of the throat, the MEMS thermal time-of-flight sensor 210 can detect the flow change of the gas timely and accurately, the measurement sensitivity of the MEMS thermal time-of-flight sensor 210 is improved, and the measurement requirement for the low-flow gas is satisfied.

Preferably, the carrier plate 230 is made of a ceramic material. With such an arrangement, the corrosion resistance of the carrier plate 230 is greatly improved, thereby prolonging the service life of the MEMS sensor assembly 200.

Preferably, the thickness of the carrier plate 230 is between 1-2 mm. By the arrangement, a boundary layer can be formed when the gas flows through the MEMS thermal time-of-flight sensor 210, so that the measurement of the gas parameters by the MEMS thermal time-of-flight sensor 210 is always carried out under the laminar flow condition, and the measurement result is accurate.

Referring to fig. 4, in the embodiment, the carrier 230 is further provided with a main connection pad 240, and the MEMS thermal time-of-flight sensor 210 and the flammable gas concentration sensor 220 are both connected to the control module 300 through the main connection pad 240.

Preferably, the MEMS thermal time-of-flight sensor 210 and the flammable gas concentration sensor 220 are connected to the control module 300 by soldering gold-plated pins or gold wires.

Referring to fig. 5, in the present embodiment, the MEMS thermal time-of-flight sensor 210 further includes a first substrate 211, the first heating element 212, the first thermal element 213, and the second thermal element 214 are all fixed on the first substrate 211, the first substrate 211 is further provided with a first temperature sensing element 215, the first temperature sensing element 215 is configured to sense an ambient temperature of the gas, and the first temperature sensing element 215 is electrically connected to the control module 300.

When the gas flowmeter is in operation, when gas flows through the MEMS thermal time-of-flight sensor 210 in the gas flow channel 100, the first temperature sensing element 215 can be used to measure the ambient temperature (gas temperature) of the gas, when the first temperature sensing element 215 senses a temperature signal of the gas, the temperature signal can be fed back to the control module 300, and the control module 300 controls the heating temperature of the first heating element 212, so that the first heating element 212 can maintain constant power or constant temperature above the ambient temperature, a stable temperature field can be ensured, the gas can be heated at corresponding temperature, and control over the heating scheme of the first heating element 212 can be provided, so as to ensure accurate measurement of corresponding parameters of the gas.

Preferably, the first substrate 211 is a silicon substrate.

Referring to fig. 5, in the present embodiment, the first substrate 211 is formed with a first thermal insulation cavity 218, wherein the first thermal insulation cavity 218 is configured to prevent heat generated by the first heating element 212 from being conducted to the first substrate 211. So configured, a degree of thermal isolation can be provided for the first heating element 212, thereby ensuring the sensitivity of the first heating element 212.

Preferably, in the present embodiment, the first thermal isolation chamber 218 is formed by ion etch back or wet chemical etch, and a low stress silicon nitride and silicon oxide composite film with a micron thickness is used as a film support.

Referring to fig. 5, in the present embodiment, a wake-up element 216 may be further disposed on the first substrate 211, specifically, the wake-up element 216 is electrically connected to the control module 300, and the wake-up element 216 is configured to wake up the control module 300 when sensing a change in the gas temperature.

So set up for when gas flows through, control module 300 just is awaken up and is gone up and get into operating condition, thereby need not to make control module 300 remain operating condition throughout, power saving and energy saving.

Preferably, in this embodiment, the wake-up element 216 is a thermopile for detecting the gas from static state to flow initiation. The detection of temperature changes by the thermopile does not require any external power source, and when the control module 300 enters sleep mode with no gas flow, the thermopile will be used to detect gas-induced temperature changes and upon detection of a change, wake up the control module 300.

Referring to fig. 5, in the present embodiment, the first heating element 212, the first thermo-sensitive element 213, the second thermo-sensitive element 214, the first thermo-sensitive element 215 and the wake-up element 216 are all connected to the control module 300 by being bonded to the first connection pad 217.

Fig. 6 is a schematic structural diagram of the combustible gas concentration sensor 220 of the gas flowmeter according to the present embodiment. As shown in fig. 6, the combustible gas concentration sensor 220 includes a second base 221, and a combustible gas concentration sensing element 222, a second heating element 223 and a second temperature-sensing element 224 which are all disposed on the second base 221, wherein the second heating element 223 and the second temperature-sensing element 224 are all electrically connected with the control module 300. Wherein the combustible gas concentration sensing element 222 comprises a metal oxide.

When the gas flowmeter is in operation, the second temperature-sensing element 224 is used for measuring the ambient temperature of the gas (gas temperature), when the second temperature-sensing element 224 senses the temperature signal of the gas, the temperature signal can be fed back to the second heating element 223, the heating temperature and the heating power of the second heating element 223 are controlled, and the combustible gas concentration sensing element 222 is raised to the temperature required by the reaction by the second heating element 223, so that the measurement of the concentration of the component with the combustion value in the gas medium is realized.

The method for measuring the concentration of the combustible gas utilizes the temperature feedback of the second temperature sensing element 224 to provide control over the heating scheme of the second heating element 223, so that the corresponding parameters of the gas can be accurately measured, and the measurement result is accurate. In addition, the arrangement is that the second heating element 223 enters the working state when the gas flows through, so that the second heating element 223 does not need to be kept in the heating state all the time, and the electricity and the energy are saved.

Preferably, the temperature at which the combustible gas concentration sensing element 222 reacts is typically between 200 and 400 ℃.

It should be noted that in actual operation, the second heating element 223 may be operated at two different temperatures to eliminate thermal drift and other adverse effects.

In the present embodiment, the combustible gas concentration sensing element 222 is made of a metal oxide such as zinc oxide, tin oxide, or tungsten oxide. Also, noble metal dopants may be added to the metal oxide film during fabrication, such as: platinum, palladium or rhodium.

In other embodiments, the combustible gas concentration sensor 220 may also use infrared sensing principles or chemical/catalytic principles or optical and acoustic sensing principles to achieve the measurement of the combustible gas concentration.

Referring to fig. 6, in the present embodiment, the second substrate 221 defines a second insulating cavity 226, wherein the second insulating cavity 226 is configured to prevent the heat generated by the second heating element 223 from being conducted to the second substrate 221. So configured, a degree of thermal isolation can be provided for the second heating element 223, thereby ensuring the sensitivity of the second heating element 223.

Preferably, the combustible gas concentration sensor 220 is also fabricated using MEMS sensing technology, and is configured such that the combustible gas concentration sensor 220 can meet low power mode and miniaturized design requirements.

Specifically, a thin film made of low stress silicon nitride and silicon dioxide may be formed on the second substrate 221, the thin film may be formed by low pressure chemical vapor deposition, the second insulating chamber 226 may be located under the thin film, and the second insulating chamber 226 may be formed by a plasma deep etching or chemical etching method.

With reference to fig. 6, in the present embodiment, the second heating element 223, the second temperature-sensing element 224 and the combustible gas concentration sensing element 222 are all connected to the main connection pad 240 of the MEMS sensor component 200 by being bonded to the second connection pad 225, so as to be electrically connected to the control module 300.

In this embodiment, the second heating element 223 and the second temperature-sensing element 224 are preferably thermistors.

Referring to fig. 1 to fig. 3, in the present embodiment, the gas flowmeter further includes a box 410 having an opening and a cover 420 for closing the opening, and specifically, the cover 420 and the box 410 are hermetically connected to form a gas buffer chamber 400. Wherein, the inlet 421 and the outlet 422 of the gas buffer chamber 400 are both opened on the cover 420.

Specifically, as shown in fig. 3, the cover 420 and the case 410 are hermetically coupled by a packing 430, and the gas meter further includes a plurality of coupling screws 440, each coupling screw 440 being used to fix the cover 420 and the case 410 together. So configured, the worker can separate the cover 420 from the case 410 to maintain the internal components thereof.

Preferably, the cover 420 and the case 410 are made of metal plates, and the metal plates may be subjected to corrosion-resistant plating or painting. Similarly, the threaded pipe of the inlet 421 and the threaded pipe of the outlet 422 are also made of metal subjected to corrosion prevention treatment. So set up, can improve the corrosion resistance of gas buffer room 400 greatly to prolong this embodiment gas flowmeter's working life.

Fig. 7 is a partial exploded view of the gas flowmeter according to the present embodiment, and fig. 8 is a partial side view of the gas flowmeter according to the present embodiment. Referring to fig. 5, and with reference to fig. 7 and 8, in the present embodiment, a gas collecting hood 150 is fixedly disposed on an outer wall of the gas channel 100, specifically, a hood opening of the gas collecting hood 150 faces a cavity of the gas buffer chamber 400, a gas collecting cavity is formed in the gas collecting hood 150, the gas collecting cavity is communicated with the gas channel 100 through an opening 160, and the carrier plate 230 is inserted into the opening 160.

When the carrier plate 230 is inserted into the opening 160, the MEMS thermal time-of-flight sensor 210 is located in the gas flow channel 100 (channel space a) and is in direct contact with the flowing gas, while the combustible gas concentration sensor 220 is held in the gas collection chamber formed by the gas collection enclosure 150, where the gas can freely exchange with the flowing medium by diffusion, but the gas is kept in a relatively stationary state, and the combustible gas concentration is measured by the combustible gas concentration sensor 220.

Through setting up gas collecting channel 150, reached the effect of gathering together gaseous for combustible gas concentration sensor 220 is surrounded by gas, promptly: the gas-collecting hood 150 is configured to allow the combustible gas concentration sensor 220 to perform sufficient exchange and measurement with gas under static conditions, so that the combustible gas concentration sensor 220 can timely and accurately measure the current combustible gas concentration.

In this embodiment, the gas collecting hood 150 may have a rectangular parallelepiped structure shown in the figure, but is not limited to this, and other arrangements may be adopted, such as: a hemispherical shape, etc., as long as the gas collecting means can collect the gas by the arrangement of the gas collecting channel 150, and the specific shape of the gas collecting channel 150 is not limited in this embodiment.

Specifically, in this embodiment, a filter may be provided at the opening 160 for communicating the gas collection enclosure 150 with the gas flow passage 100, wherein the filter is configured to filter the gas flowing from the gas flow passage 100 to the gas collection chamber. So set up, impurity such as can filter off oil gas, granule or other foreign matters effectively for combustible gas concentration sensor 220 has the best test environment, has reduced impurity to combustible gas concentration sensor 220's adverse effect, has guaranteed the accuracy nature of the data that record.

Referring to fig. 3, in the present embodiment, the gas flow channel 100 may include a main flow channel 110 and a connecting flow channel 120 sequentially arranged along a gas flow direction, wherein the main flow channel 110 is in a straight tube shape, the connecting flow channel 120 is in a bent tube shape, and the connecting flow channel 120 is used for connecting with an outlet 422 of the gas buffer chamber 400; the MEMS thermal time-of-flight sensor 210 is located within the primary flow channel 110.

By providing the gas flow channel 100 as the main flow channel 110 and the connecting flow channel 120, on one hand, the stability of the gas flowing in the straight tubular main flow channel 110 can be utilized to accurately measure the corresponding parameters of the gas, and on the other hand, the connecting flow channel 120 in the bent tubular shape can be utilized to realize the connection with the outlet 422, thereby facilitating the assembly of the gas flow channel 100 and the gas buffer chamber 400.

Preferably, the main runner 110 is formed by injection molding of corrosion-resistant engineering plastic such as polycarbonate, and the material and the manufacturing process of the connecting runner 120 are the same as those of the main runner 110.

Preferably, the bending angle of the connection flow path 120 is 90 °.

Referring to fig. 3 and fig. 7, in the present embodiment, the diameter of the air inlet end 130 of the primary flow channel 110 is larger than the diameter of the main body of the primary flow channel 110. When gas enters the main flow passage 110 from the gas buffer chamber 400, since the diameter of the gas inlet end 130 is larger than the diameter of the main body of the main flow passage 110, that is: the flow area will be reduced, thereby accelerating the flow rate of the gas, so that the primary flow channel 110 has a better and more stable flow field at a low flow rate.

Preferably, the diameter of the inlet end 130 is 1.2-1.5 times the main diameter of the primary flowpath 110.

Referring to fig. 3, in the present embodiment, an anti-corrosion gasket 170 is connected between the main flow channel 110 and the connecting flow channel 120. With the arrangement, the sealing connection between the main flow channel 110 and the connecting flow channel 120 is realized, and the leakage of gas is avoided, and the arrangement of the anti-corrosion gasket 170 also enables the joint of the main flow channel and the connecting flow channel to have certain corrosion resistance, so that the service life of the gas flow channel 100 is prolonged.

Referring to fig. 3, in the present embodiment, the gas flowmeter may further include an electric valve 600, specifically, the electric valve 600 is disposed at the inlet 421, the electric valve 600 is connected to the communication unit 020, and the electric valve 600 is configured to cut off the air supply at the inlet 421 when the condition is set.

When an emergency such as an earthquake occurs, the electrically operated valve 600 can cut off the gas supply through the remote communication of the communication unit 020 or the control of the control module 300 to prevent the gas leakage, thereby ensuring the safety performance of the gas flowmeter of the present embodiment.

In addition, the electrically operated valve 600 can be used as a local or remote prepayment actuator. Specifically, such as: when the user owes the fee, the electric valve 600 can be cut off through remote communication, and the gas supply is blocked, so that the user is prompted to pay the fee.

It should be noted that in the normal operation state of the gas flowmeter, the electric valve 600 may be kept in the normally open state.

Referring to fig. 3, in the present embodiment, the electric valve 600 is located in the gas buffer chamber 400, and a connection gasket 180 is disposed between the electric valve 600 and the inlet 421 of the gas buffer chamber 400, and similarly, a connection gasket 180 is also disposed between the connection channel 120 and the outlet 422 of the gas buffer chamber 400. By the arrangement, the tightness of the inlet 421 and the outlet 422 of the gas buffer chamber 400 is ensured, and the leakage of gas is avoided.

Preferably, the connection washer 180 is made of a corrosion-resistant material. With this configuration, the service life of the connection gasket 180 can be prolonged, thereby prolonging the service life of the gas flowmeter of the present embodiment.

With continued reference to fig. 3 and 7, in the present embodiment, the gas inlet 130 of the gas channel 100 may be provided with a flow field regulator 700.

When the gas flowmeter is used, gas passes through the flow field regulator 700 before entering the gas flow channel 100, and turbulence and unstable fluctuation are eliminated by using the flow field regulator 700, so that interference to a measurement process is reduced, and the measurement accuracy is ensured.

Referring to fig. 3, in particular, in the present embodiment, the flow field regulator 700 is formed by a grid.

Fig. 9 is a partial structural sectional view of the gas flowmeter provided in the present embodiment. Referring to fig. 8 and fig. 9, in the present embodiment, a flow distributor 500 may be further disposed in the main flow channel 110, specifically, the flow distributor 500 includes a plurality of coaxial tubes 510 sequentially sleeved, and a distance between any two adjacent coaxial tubes 510 is not greater than a diameter of the coaxial tube 510 located at the most central position. The flow distributor 500 is used to further stabilize the flow while ensuring the required flow dynamic range to further improve the stability of the flow field.

Referring to fig. 9, in the present embodiment, the axial length of the flow distributor 500 is not less than 1/3 of the axial length of the main flow channel 110. So set up, can realize the reliable distribution to the flow to the regulatory effect to the flow field has been guaranteed.

Referring to fig. 1 to fig. 3, in the present embodiment, the communication unit 020 includes a front cover 810, a rear cover 820 and a display module 800, specifically, the front cover 810 and the rear cover 820 are connected to form an accommodating cavity, the display module 800 is disposed in the accommodating cavity, the front cover 810 is provided with a first window 811 opposite to the display module 800, and the first window 811 is covered with a transparent panel 830, where the transparent panel 830 has a data tamper-proofing function.

The setting of the display module 800 enables a user to observe current flow information in real time, and the transparent panel 830 with a data tamper-proof function is arranged at the first window 811, so that malicious tampering of data can be avoided, and the use safety of the gas flowmeter in the embodiment is ensured.

Specifically, in this embodiment, the transparent panel 830 may be made of glass or plastic, and the tamper-resistant transparent metal film coating covers the transparent panel, so as to achieve the purpose of preventing data from being tampered.

Preferably, the Display module 800 is made of a low power LCD (Liquid Crystal Display).

Referring to fig. 3, in the present embodiment, the communication unit 020 further includes a battery power module 900, wherein the battery power module 900 is disposed in the accommodating cavity, the front cover 810 further defines a second window 812 opposite to the battery power module 900, and the second window 812 is detachably covered with a battery chamber cover 840.

By providing the battery power module 900, independent power supply to the communication unit 020 and the control module 300 is realized. It should be noted that for some communication protocols requiring high power, the battery power module 900 is only used to power the metering unit 010 and the control module 300 of the gas flow meter, and for communication, is powered by an external power source through a data port, which may be integrated into the printed circuit board of the display module 800.

In this embodiment, the bezel 810 may also be provided with user operable keypads for password controlled local flow meter parameter setting, data access, diagnostics, and third party calibration or meter correction. The remote data communication module in the communication unit 020 is preferably in the form of a replaceable module integrated on the same printed circuit board as the display module 800. The remote data communication preferably operates over communication standard protocols such as NB-IoT or GPRS or others depending on the installation of the gas meter.

In other embodiments, the remote data communication may also adopt a wireless manner or a wired manner, such as bluetooth, Zigbee, LoRa, infrared transmission, and the like.

Referring to fig. 3, in the present embodiment, the control module 300 is electrically connected to the communication power source through the sealed cable 030, wherein the sealed cable 030 is installed on the box 410. This configuration is compatible with existing utility gas meter mechanical connections and enables seamless installation and replacement of existing gas meters on existing gas pipelines.

The working principle of the gas flowmeter is as follows: the electric valve 600 is kept in an open state, and gas enters through the inlet 421 of the gas buffer chamber 400 and gradually fills the gas buffer chamber 400; then, the gas in the gas buffer chamber 400 enters the gas channel 100 through the gas inlet 130, when the wake-up element 216 in the MEMS thermal time-of-flight sensor 210 senses a change in the gas temperature, the control module 300 is woken up, the control module 300 correspondingly controls the first temperature sensing element 215, the first heating element 212, the first temperature sensing element 213, and the second temperature sensing element 214, so as to collect the mass flow and the volume flow of the gas, and calculate the current thermal conductivity, the specific heat capacity, and other thermal parameters of the gas according to the collected mass flow and volume flow. Meanwhile, when the second temperature sensing element 224 senses the temperature change of the gas, the second heating element 223 is awakened, the second heating element 223 is used for providing heat required by the reaction for the combustible gas concentration sensing element 222, the concentration of the component with the combustion value in the gas is measured, so that the conversion of the thermal property of the gas into the high calorific value is performed, and the data is stored in the memory of the control module 300. Wherein the data in the memory can be downloaded through a local data port, and at the same time, the data can be transmitted to a designated data or service center through remote data communication, and the corresponding event code can be displayed on the display module 800 of the gas flow meter.

In this embodiment, the number of the memories is preferably not less than three, and each memory is used for storing data information to prevent a device failure. Wherein the data in the memory can be retrieved online or transmitted to a designated data or service center at user-determined intervals. The external card reader may further retrieve the stored data through a local data port. The MCU will compare these data from time to time and once any discrepancies, events or alarms will be registered and stored in different memories that can be retrieved on site and, if the gas meter is connected to the network, transmitted to a designated data or service center.

It should be noted that the control module 300 may also have other functions, such as: detect battery power module 900 status, flow anomalies, and perform other pre-programmed tasks of interest to the user.

The gas flowmeter disclosed in the present embodiment has the same communication means 020 between the models, and is manufactured in accordance with the international utility gas meter standard only in accordance with the full range required for the application, depending on the mechanical parameters such as the size of the gas buffer chamber 400, the size of the threaded pipe for the inlet 421 and the outlet 422, and the distance from the inlet 421 to the outlet 422. Also, the respective dimensions of the internal mechanical components such as the electric valve 600 and the gas flow channel 100 will be adjusted accordingly, but all the electronic components are identical. Fig. 1 and fig. 2 respectively show two typical examples, wherein fig. 1 is a commercial gas meter with 50mm diameter of inlet 421/outlet 422 threaded pipe, which is equivalent to a mechanical G25 model; FIG. 2 shows a domestic gas meter with inlet 421/outlet 422 threaded pipes of 30mm diameter.

To city natural gas trade measurement or other relevant gaseous measurement, the utility model provides an accurate measurement scheme, the irrelevant measurement standard of present gaseous component of this scheme compatibility and rate system have automatic temperature and pressure compensation's advantage simultaneously. The measured gas heat value and related gas composition data are beneficial to the upgrade of a future heat value or energy price metering system. This data will help to justify the evaluation of the supply chain system even with current billing regimes. The gas flowmeter can record data and manage remotely through a network without additional mechanical-electronic data conversion, thereby not only reducing the cost, but also ensuring the data accuracy and safety. In addition, the gas flowmeter also allows the seamless replacement and installation of the existing mechanical flowmeter without additional modification, and is convenient for construction.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one of ordinary skill in the pertinent art without departing from the scope or spirit of the present invention, and the scope of the present invention is defined by the appended claims.

Finally, it should also be noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

In the above embodiments, the descriptions of the orientations such as "up", "down", and the like are based on the drawings.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A gas flow meter, characterized by comprising a metering unit (010) and a communication unit (020); the metering unit (010) comprises a gas flow channel (100), an MEMS sensor assembly (200) and a control module (300), wherein the gas flow channel (100) provides a stable flow field of the detected gas; the MEMS sensor assembly (200) comprises a MEMS thermal time-of-flight sensor (210) and a combustible gas concentration sensor (220), wherein the MEMS thermal time-of-flight sensor (210) and the combustible gas concentration sensor are electrically connected with the control module (300), the MEMS thermal time-of-flight sensor comprises a first heating element (212) and a plurality of heat-sensitive elements which are sequentially arranged along the gas flow direction, the distance between at least two of the heat-sensitive elements and the first heating element (212) is in non-integral multiple relation, and the combustible gas concentration sensor (220) is configured to measure the concentration of a component with a combustion value in gas; the communication unit (020) is electrically connected with the control module (300).

2. The gas meter according to claim 1, further comprising a gas buffer chamber (400), wherein the gas buffer chamber (400) has an inlet (421) and an outlet (422), the gas flow channel (100) is disposed in the gas buffer chamber (400), and the gas outlet (140) of the gas flow channel (100) is connected to and in communication with the outlet (422), and the gas inlet (130) of the gas flow channel (100) extends into the gas buffer chamber (400); the inlet (421) and the outlet (422) open to the same surface of the gas buffer chamber (400).

3. The gas meter according to claim 2, wherein the MEMS sensor assembly (200) further comprises a carrier plate (230), the MEMS thermal time-of-flight sensor (210) and the combustible gas concentration sensor (220) are both fixed to the carrier plate (230), the carrier plate (230) is inserted into the gas flow channel (100), the MEMS thermal time-of-flight sensor (210) is located in the gas flow channel (100), and the combustible gas concentration sensor (220) is located outside the gas flow channel (100) and in the gas buffer chamber (400).

4. A gas meter as claimed in claim 3, wherein the gas flow conduit (100) is venturi-shaped, the MEMS thermal time-of-flight sensor (210) being located centrally in the throat of the gas flow conduit (100).

5. The gas flowmeter of claim 3, wherein a gas collecting hood (150) is fixedly arranged on the outer wall of the gas flow channel (100), a hood opening of the gas collecting hood (150) faces the cavity of the gas buffer chamber (400), a gas collecting cavity is formed in the gas collecting hood (150), the gas collecting cavity is communicated with the gas flow channel (100) through an opening (160), and the carrier plate (230) is inserted into the opening (160).

6. A gas meter as claimed in claim 5, wherein a filter is provided at the opening (160), the filter being configured to filter gas flowing from the gas flow passage (100) to the gas collection chamber.

7. A gas meter according to any of claims 2-6, wherein the gas flow channel (100) comprises a main flow channel (110) and a connecting flow channel (120) arranged in sequence along the gas flow direction, the main flow channel (110) is straight-tube shaped, the connecting flow channel (120) is bent-tube shaped, and the connecting flow channel (120) is used for connecting with the outlet (422); the MEMS thermal time-of-flight sensor (210) is located within the primary flow channel (110).

8. The gas flowmeter of claim 7, wherein a flow distributor (500) is disposed in the main flow channel (110), the flow distributor (500) comprises a plurality of coaxial tubes (510) sequentially sleeved, and a distance between any two adjacent coaxial tubes (510) is not greater than an inner diameter of the coaxial tubes (510) located at a centermost position.

9. The gas meter of claim 8, wherein the axial length of the flow distributor (500) is no less than 1/3 of the axial length of the primary flow passage (110).

10. Gas meter according to any of claims 2-6, further comprising an electrically operated valve (600), the electrically operated valve (600) being arranged at the inlet (421), the electrically operated valve (600) being electrically connected to the communication unit (020), the electrically operated valve (600) being configured to shut off the gas supply at the inlet (421) when setting a condition.

11. A gas meter as claimed in any of claims 1 to 6, characterized in that the gas inlet end (130) of the gas flow channel (100) is provided with a flow field regulator (700).

12. The gas flowmeter of any of claims 1-6, wherein the communication unit (020) comprises a front cover (810), a rear cover (820), and a display module (800), wherein the front cover (810) is connected with the rear cover (820) to form a containing cavity, the display module (800) is arranged in the containing cavity, the front cover (810) is provided with a first window (811) opposite to the display module (800), the first window (811) is covered with a transparent panel (830), and the transparent panel (830) has a data tamper-proofing function.

13. The gas flowmeter of claim 12, wherein the communication unit (020) further comprises a battery power module (900), the battery power module (900) is disposed in the accommodating cavity, the front cover (810) further defines a second window (812) opposite to the battery power module (900), and the second window (812) is detachably covered with a battery chamber cover (840).

14. The gas meter according to any of claims 1-6, wherein the MEMS thermal time-of-flight sensor (210) further comprises a first substrate (211), the number of the thermal elements is two, and the first heating element (212) and both the thermal elements are fixed to the first substrate (211); the first base (211) is further provided with a first temperature sensing element (215), the first temperature sensing element (215) is configured to sense an ambient temperature of the gas, and the first temperature sensing element (215) is electrically connected with the control module (300).

15. A gas meter as claimed in claim 14, characterized in that the first base body (211) is further provided with a wake-up element (216), the wake-up element (216) being electrically connected with the control module (300), the wake-up element (216) being configured to wake-up the control module (300) upon sensing a gas temperature change.

16. A gas meter as claimed in any one of claims 1 to 6, characterised in that the combustible gas concentration sensor (220) comprises a second substrate (221) and a combustible gas concentration sensing element (222), a second heating element (223) and a second temperature-sensitive element (224) each provided to the second substrate (221), the second heating element (223) and the second temperature-sensitive element (224) each being electrically connected to the control module (300).